diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index be6c083..8a72a39 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -13,8 +13,8 @@ jobs:
       fail-fast: false
       matrix:
         ruby-version:
-          - "3.2"
-          - "3.3"
+          - "3.4"
+	  - "4.0"
 
     steps:
       - name: Checkout
diff --git a/Gemfile.lock b/Gemfile.lock
index cea688b..40fa269 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -3,7 +3,7 @@ GEM
   specs:
     dotenv (3.2.0)
     drb (2.2.3)
-    minitest (6.0.2)
+    minitest (6.0.3)
       drb (~> 2.0)
       prism (~> 1.5)
     prism (1.9.0)
@@ -21,7 +21,7 @@ DEPENDENCIES
 CHECKSUMS
   dotenv (3.2.0) sha256=e375b83121ea7ca4ce20f214740076129ab8514cd81378161f11c03853fe619d
   drb (2.2.3) sha256=0b00d6fdb50995fe4a45dea13663493c841112e4068656854646f418fda13373
-  minitest (6.0.2) sha256=db6e57956f6ecc6134683b4c87467d6dd792323c7f0eea7b93f66bd284adbc3d
+  minitest (6.0.3) sha256=88ac8a1de36c00692420e7cb3cc11a0773bbcb126aee1c249f320160a7d11411
   prism (1.9.0) sha256=7b530c6a9f92c24300014919c9dcbc055bf4cdf51ec30aed099b06cd6674ef85
   rake (13.3.1) sha256=8c9e89d09f66a26a01264e7e3480ec0607f0c497a861ef16063604b1b08eb19c
 
diff --git a/README.md b/README.md
index 0dd4178..431aa59 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![CI](https://github.com/koichiro/codex-notify/actions/workflows/ci.yml/badge.svg)](https://github.com/koichiro/codex-notify/actions/workflows/ci.yml)
 [![Coverage](https://img.shields.io/badge/coverage-80%25-brightgreen)](#development)
-[![Ruby](https://img.shields.io/badge/ruby-3.2%2B-red)](#development)
+[![Ruby](https://img.shields.io/badge/ruby-3.4%2B-red)](#development)
 [![License: MIT](https://img.shields.io/badge/license-MIT-yellow.svg)](./LICENSE)
 
 `codex-notify` is a small Ruby CLI tool that posts compact Slack notifications from Codex.